The present disclosure relates generally to an arrangement for, and a method of, detecting passage of objects associated with radio frequency (RF) identification (RFID) object tags through a portal that is openable and closable by a door movable between respective open and closed positions at a venue.
Radio frequency (RF) identification (RFID) technology is becoming increasingly important for logistics concerns, material handling and inventory management in retail stores, warehouses, distribution centers, buildings, and like venues. An RFID system typically includes a plurality of RFID readers, also known as interrogators, deployed about a venue. Each RFID reader interrogates multiple RFID object tags in its coverage range. Each object tag is usually attached to, or associated with, an individual object or item, or to a package for the item, or to a pallet or container for supporting or containing multiple items. Each object tag typically includes a tag antenna for receiving and/or transmitting RF waves, and an integrated circuit chip that typically has a power management section, a radio section, and frequently a logic section containing a control microprocessor, a memory, or both. Each RFID reader transmits an RF interrogating signal, and each object tag, which senses the interrogating RF signal with its tag antenna, responds by transmitting a return RFID receive signal from its tag antenna. The object tag either generates the return RFID receive signal originally, or reflects back a portion of the interrogating RF signal in a process known as backscatter. The return RFID receive signal may be decoded into data by each reader, which thereby identifies, counts, or otherwise interacts with the associated object, and/or can be used for locationing applications, i.e., for estimating and determining the location or bearing, i.e., the angular direction both in azimuth and elevation, of any particular object and its object tag relative to a particular reader or readers by triangulation/trilateration techniques known in the art.
In such venues, it is sometimes necessary to accurately determine which RFID-tagged objects inside the venue have exited the venue, e.g., have passed through a portal, which is openable and closable by a door, to the outside of the venue. An interior RFID reader inside the venue and proximal to the portal is typically able to read object tags that approach the portal. However, the interior RFID reader, by itself, cannot always accurately determine whether any particular RFID-tagged objects have actually passed through the portal. For example, it is possible that a particular RFID-tagged object has been advanced to be near the portal, but has been backed away from the portal without ever passing therethrough. It is also possible that the RFID-tagged objects are just unreadable by the interior RFID reader. As a result, the RFID system may not always accurately know which and how many RFID-tagged objects have actually exited the venue.
For greater accuracy, another RFID reader could be mounted outside the venue to read any RFID-tagged objects that have passed through the portal. However, this involves positioning antennas at, and routing cables to, the exterior of the venue. Holes may have to be drilled through walls of the venue, and any such holes would typically need to be properly sealed. In addition, the antennas and the cables typically need to be weatherized, armored, and protected from vandalism since they are exposed outside the venue. The installation of such an exterior RFID reader can be cost prohibitive, especially for smaller venues.
Accordingly, there is a need to accurately and inexpensively determine which and how many RFID-tagged objects have actually passed through the portal without having to install hardware, such as RFID readers, outside the venue.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions and locations of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The arrangement and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.